1. Field of the Invention
The present invention relates to inkjet recording heads that discharge ink towards a recording face of a recording medium to perform a recording operation. In particular, the present invention relates to an inkjet recording head in which a flexible film substrate is mounted on a substrate that holds recording elements for generating energy used for discharging ink.
2. Description of the Related Art
Inkjet recording apparatuses are recording apparatuses of a non-impact recording type and are greatly advantageous in terms of releasing almost no noise during recording and having the capability to record high resolution images on various kinds of recording media at high speed. U.S. Pat. No. 6,863,381 discloses an example of an inkjet recording apparatus. In the inkjet recording apparatus disclosed in U.S. Pat. No. 6,863,381, ink-discharging nozzle arrays are disposed adjacent to only one side of supply ports provided in a recording-element substrate (heater chip). In addition, regarding these supply ports in the recording-element substrate, the distance from a long edge of a first outermost supply port to a first edge of the recording-element substrate is different from the distance from a long edge of a second outermost supply port to a second edge of the recording-element substrate.
An inkjet recording head typically used in an inkjet recording apparatus generally has nozzle plates each equipped with small ink discharge nozzles (which will simply be referred to as nozzles hereinafter). An inkjet recording head also has a recording-element substrate equipped with a plurality of discharge-energy generating elements that apply discharge energy to a liquid flow passage and to recording liquid within the liquid flow passage. A surrounding area around the recording-element substrate and a part of an electrical connection between the recording-element substrate and a flexible film wiring substrate are coated with a sealant. This sealant protects these elements from corrosion caused by the recording liquid, from short circuit, and from an external force applied during, for example, wiping.
With the advancement in recording technologies in recent years, the inkjet technology needs to have the capability to record higher resolution images. To achieve this, inkjet recording heads require extremely small nozzles.
However, the aforementioned recording head has the following problems. Specifically, after the sealant is applied on the recording-element substrate, the sealant shrinks as it becomes cured. The stress produced by this shrinkage of the sealant can cause deformation of the nozzle plates and the nozzles. The deformation is especially conspicuous at the outermost nozzle arrays on the recording-element substrate, and can be even more influential if the nozzles are extremely small in size. The deformation leads to inconsistency in the discharging direction of ink droplets, resulting in unevenness of the ink density on the output image. Especially in the case of U.S. Pat. No. 6,863,381 where the recording-element substrate has the discharge-energy generating elements disposed adjacent to only one side of the supply ports and has the supply ports arranged such that the long edges of the outermost supply ports and the opposite edges of the recording-element substrate are spaced apart by asymmetrical distances, the following problems tend to occur. The effect of shrinkage stress of the sealant at the side with the relatively shorter distance is greater than that at the side with the relatively longer distance. As a result, the degree of deformation of the nozzle plates and the nozzles may be unbalanced between the two sides. Minimizing the deformation of the nozzles can be achieved by reducing the effect the shrinkage effect of the sealant has on the nozzles. This can be done by reducing the width of the sealant. However, if the sealant is to be reduced in width, it may make it difficult for the sealant to flow when it is being applied onto the recording-element substrate, which can possibly lead to an increase in manufacturing tact time in the sealant application process performed at the time of production of inkjet heads, the sealant application process including, for example, emission control and positional adjustment of the sealant. In addition, simply reducing the width of the sealant can cause deformation of the nozzles due to a difference in shrinkage stress of the sealant between the opposite edges of the recording-element substrate.